The disclosure relates generally to a reciprocating pump. More particularly, the disclosure relates to a hydraulically actuated reciprocating pump having a piston driven to reciprocate within a cylinder by fluid pressure. The disclosure also relates to systems and methods for reducing pressure pulsations created within the pump by reciprocation of the piston within the cylinder.
To form an oil or gas well, a bottom hole assembly (BHA), including a drill bit, is coupled to a length of drill pipe to form a drill string. The drill string is then inserted downhole, where drilling commences. During drilling, fluid, or “drilling mud,” is circulated down through the drill string to lubricate and cool the drill bit, to pressurize the borehole, and to provide a vehicle for removal of drill cuttings from the borehole. After exiting the bit, the drilling fluid returns to the surface through the annulus formed between the drill string and the surrounding borehole wall. Instrumentation for taking various downhole measurements and communication devices are commonly mounted within the drill string. Many such instrumentation and communication devices operate by sending and receiving pressure pulses through the annular column of drilling fluid maintained in the borehole.
Mud pumps are commonly used to deliver drilling fluid to the drill string during drilling operations. Many conventional mud pumps are reciprocating pumps, having at least one piston-cylinder assembly driven by a crankshaft and hydraulically coupled between a suction manifold and a discharge manifold. During operation of the mud pump, the piston is mechanically drive to reciprocate within the cylinder. As the piston moves to expand the volume within the cylinder, drilling fluid is drawn from the suction manifold into the cylinder. After the piston reverses direction, the volume within the cylinder decreases and the pressure of drilling fluid contained with the cylinder increases. When the piston reaches the end of its stroke, pressurized drilling fluid is exhausted from the cylinder into the discharge manifold. While the mud pump is operational, this cycle repeats, often at a high cyclic rate, and pressurized drilling fluid is continuously fed to the drill string at a substantially constant rate.
Because the piston directly contacts drilling fluid within the cylinder, loads are transmitted from the piston to the drilling fluid. Due to the reciprocating motion of the piston, the transmitted loads are cyclic, resulting in the creation of pressure pulsations in the drilling fluid. The pressure pulsations may disturb the downhole communication devices and instrumentation by degrading the accuracy of measurements taken by the instrumentation and hampering communications between downhole devices and control systems at the surface. Over time, the pressure pulsations may also cause fatigue damage to the drill string pipe and other downhole components.
Accordingly, there is a need for an apparatus or system and associated method that reduces pressure pulsations created within fluid pressurized by a reciprocating pump due to contact between the pump piston and the fluid.